Multipoint communication, in particular, multipoint communication over the Internet, is broadly performed by a multicast method for simultaneously delivering the same content to all participating nodes in session. Due to the complexity of intermediate node configuration, end node configuration and requirements for internet service provider participation for enabling IP layer multicasting, widespread of IP (internet protocol) multicast has been hampered.
On the other hand, a new mechanism, called “application layer multicasting (ALM),” has been known. ALM is becoming popular due to its simplicity of application layer implementation on an existing unicast network architecture. ALM allows AV (Audio Video) packet forwarding by members themselves among participating nodes because of no need for multicast forwarding function in the IP layer. In addition, ALM allows flexible AV packet forwarding in the application layer.
With ALM, AV contents or streams can be exchanged among all participants in a specific session without prior environmental setting. Therefore, ALM is very useful for AV-based applications such as video conferencing between a plurality of parties (see Patent Literatures 1, 2 and 3).
With ALM, since packet routing is performed in the application layer, each participating node has to form a source-based tree for data packet distribution. That is, with ALM, N participating nodes constructs a distribution tree of N source contents in the application layer in order to perform N-to-N communication.
On the other hand, a network layer routing mechanism is a selection mechanism solely based on measured latency (e.g. round-trip time), so that it is difficult to provide solutions for fair bandwidth allocation. Here, the network layer routing mechanism includes “minimum spanning tree (MST)” which is based on “greedy” concept of Dijkstra, Bellman-Ford and Prim algorithms for shortest path formation.
In addition, Non-Patent Literature 1 discloses a bandwidth allocation method for a plurality of streams, based on user preference, for example, wish to prioritize an interested video.
Unicast packet routing on the Internet forms shortest path based on the above-described algorithms and does not reflect ALM routing requirement. Thus, these solutions are best for network layer unicast routing but not for ALM-based application.
Citation List
Patent Literature
    [PTL 1] U.S. Patent Application Publication No. 2005/0163224    [PTL 2] U.S. Patent Application Publication No. 2006/0153100    [PTL 3] U.S. Patent Application Publication No. 2007/0133413Non-Patent Literature    [NPL 1] Puneet Mehra et al. “Receiver-driven bandwidth sharing for TCP”, Proceedings of IEEE Transactions on Multimedia, Volume 7, Issue 4, August 2005